how to store data in a matrix?

Question

Lilya 2019-7-17

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/472079-how-to-store-data-in-a-matrix

评论： Lilya 2019-7-17

Hi all,

I want to loop over the third dimension of the 3D matrix and calculate the average then sore the resulted data in a new matrix.

For example:

 U10_series = [];
    for day=1:length(datenum_array); % this time is corresponding to the number of days 
  filename=strcat('./MERRA2_400.tavg1_2d_ocn_Nx.2019',num2str(datevec_array(day,2),'%02i'),num2str(datevec_array(day,3),'%02i'),'.SUB.nc'); 
    %read U10
    U10          = ncread(filename,'U10M');
    U10_box      = U10(lon_range,lat_range,:);
    U10_box_mean = nanmean(U10_box,3);
    U10_series   = [U10_series,U10_box_mean];
end 

where am I mistaken?

The help is much appreciated

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Answer 1

KSSV 2019-7-17

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/472079-how-to-store-data-in-a-matrix#answer_383516

在 MATLAB Online 中打开

U10 = ncread(filename,'U10M');

If your variable U10M is 3D, the above line reads complete data. Your U10 should be 3D. Now you can apply mean on it by specifying the dimension you want.

Also read about ncread, here you can specify the 3D dimension you want to read in a loop. If it is not clear, attach your file for further help.

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KSSV 2019-7-17

在 MATLAB Online 中打开

ncfiles = dir('*.nc') ; 
N = length(ncfiles) ; 
for i = 1:N
    ncfile = ncfiles(i).name ;
    lon = ncread(ncfile,'lon') ; 
    lat = ncread(ncfile,'lat') ; 
    u = ncread(ncfile,'U10M') ; 
    v = ncread(ncfile,'V10M') ; 
    % do what you want 
end